[Comparative studies on the embryotoxicity of 2-methyl-4-chlorophenoxyacetic acid, mecoprop and dichlorprop in NMRI mice]

From the group of herbicidal phenoxy carbonic acids, 2-methyl-4-chlorophenoxyacetic acid (MCPA; 0-500 mg/kg), 2-(4-chloro-2-methyl-phenoxy) propionic acid (mecoprop/MCPP; 0-700 mg/kg) and 2-(2,4-dichlorophenoxy) propionic acid (dichlorprop/2,4-DP; 0-500 mg/kg) as well as the dextrorotatory compounds of MCPP (MCPPD; 0-500 mg/kg) and 2,4-DP (2,4-DPD; 0-500 mg/kg) were studied in NMRI mice after oral administration between days 6-15 of pregnancy. All five substances proved to be embryotoxic and teratogenic in varying intensity. MCPA proved to be most effective: it was embryotoxic from doses of 100 mg/kg and teratogenic from 200 mg/kg. The remaining compounds (MCPP, MCPPD, 2,4-DP, 2,4-DPD) were embryotoxic from doses of 300 mg/kg and caused malformations of the skeleton from 400 mg/kg. The embryocidal and teratogenic potencies of the dextrorotatory components of MCPA and 2,4-DP exceeded those of the corresponding racemates. Influences of MCPPD and 2,4-DPD upon postimplantative loses, frequency of cleft palates and wavy ribs appeared already at dosages being 100-200 mg/kg below those of the racemates given to the respective groups of experimental animals. Additional alterations of the skeleton were observed which did not occur following administration of the racemic mixtures: deformed centrums of thoracic vertebra and exencephaly.